As a daily React user for 10 years, and having used Ember, Angular, and several backend frameworks, I really don't agree. Hooks were the only meaningful change I can think of, and they took me about a day of real effort to grok, and a week to begin using well - in my existing React codebases no less. The primary way React works is unchanged since the very first day I learned it. It and SQL are probably the oldest tools I have at this point, and the ones that keep paying off year after year.